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Upgrading GE Delta S / SX - HF, VHF Trunk Mount - Narrow / Wideband Radios

With Integral CTCSS Encoding / Decoding

    Here's how to convert GE Delta radios for 'frequency agile' use on 10, 6, and 2 meters, or for 440 Mhz.   Service manual links are included.
Review these instructions before starting.  Don't attempt the modification if you don't feel that you can accomplish it satisfactorily or safely.  Once the conversion is done, the Delta can be used in vehicles only with a negative ground battery

 This conversion is disciplined, but not difficult.  Once done, you'll have a 100 watt, high quality FM radio of which you can be proud.

    Important Note: Check to see if your unit has the 'channel guard / voice guard' board in the front.  This board is used to:

    If you don't have this board, you can do the conversion but your Delta won't be able to identify the received tone, and you may hear the received ctcss audio tone on some transmissions (depending upon the level set by the transmitting station).  Normally, this will not be objectionable.  On the 'plus side', you will still be able to generate the ctcss tones needed to access your favorite repeaters.  You probably will not have any talk off problems.

Also Note: This website shows pictures of a Delta conversion without the internal CTCSS board.  When you are making the interface connections, be sure to leave enough space and wire 'slack' to properly reinstall the channel guard board when you are ready to test.

    a) General Conversion Information - Schematic

     The external M/P replaces the frequency selection functions of the Delta's internal M/P.  The leads connecting to the Delta's frequency synthesizer will be 'disconnected'.  In turn, the external M/P 'channels' the PLL for receive and transmit operation and manages the CTCSS tones.

 Three conversion techniques are described:

Note: Since Delta radios use CMOS technology, follow safe CMOS handling procedures.  Use a grounded soldering iron, not a gun.

  b) Constructing The Control Head and Interfacing With the Delta Radio

    A control head needs to be built -  the components are available.  A large Radio Shack plastic enclosure can house the P/C board, the keypad, LCD, the volume control (with an OFF / ON switch), a mike jack and a small speaker.  When not needed, the control head can be stored out of sight. 

    The head may be used with several different radios of the same or different frequency if the pin assignment convention is the same.  Since the M/P uses flash memory, it's easy to change the radio interface with a few key presses.

c) Powering Considerations

    There are two sources of 13.8 VDC power to the Delta.  The first is the high current source required to power the transmitter PA stage up to 110 watts.  The second is the low current source required by the receiver and common electronics.

     The fused low current 12 VDC lead (say, from your car's ignition switch) that runs to pin 19 on  P / J-601 can be brought to the control head and activated by a switch on the volume control.  This switched 12 VDC source will also be needed for the new M/P board.   If this powering technique is used, then no other power leads within the DB-25 cable are required.    

    Or, a small  remote power relay may be placed in the Delta, permitting the removal of the control head when not in use. Placing a ground on pin 17 of the DB-25 cable will operate the relay and provide power to both the Delta (on J-601, pin 19) and to the Control Head (on pin 3 of the DB-25 cable).  These radios draw considerable current on receive and can render a car - whose battery is not charging - incapable of starting in short order.

d) Using the Delta's Internal Squelch Control 

    You may want to use the Delta's Internal Squelch Control, if it has one. First, check to see if your Delta has an internal squelch control (service manual). The control is R666 and near the front of the Control Board.  If present - remove P-605.  

    If your radio does not have R666, you may add one. Ground one end of a 10K control, and connect the center wiper to pin 3 of J-605.  Connect the hot end of the control to J-608, pin 2.  It can be epoxied inside the Delta. 

e) Steps Common to All Conversion Techniques

Note: These pins will serve as either convenient connection points of your choosing (for either of the DB-25 conversions)shown here.


f) DB-25 Drill Conversion

g) DB-25 No-Drill Conversion

    This involves removing first the control board from the radio and then the battery and ground connections through which permanent power and ground leads will be routed.  There's no need to drill separate holes in the radio. However,  if done incorrectly, there could be damage of surface mount components.  

    Please become familiar with the process:

h) Complete Either DB-25 Conversion


i) Preliminary Tests

    Ensure that all connections are correct.  A  test table provides resistance and voltage measurements at each of the DB-25 connector pins.

    Make the resistance tests from the chassis to each of the pins in the DB-25 connector.  They should all be close.  Correct, as needed. 

    Next, apply power to the Delta by either:

     Measure the voltages at each of the pins.  When done, remove the power / ground.

j) Connect the Control Head

    You'll have to build up a control head, and the required components are available.  A large Radio Shack plastic enclosure works perfectly as it can house the P/C board, the keypad, LCD, the volume control (with an OFF / ON switch), a mike jack and even a small speaker.  

    A 'connectorized' control head may be used with several radios of the same or different frequency if the pin assignment convention is the same for each.  Since the new M/P uses flash memory, it's easy to change the radio interface.  See suggestions on Control Head construction.

    Note: You may program channels used in any of these radios into their respective 'banks'.  There are 5 banks of 20 channels each.

    With the power off, connect the Control Head to the DB-25 cable.  If you have the time, double check the end to end connections with your meter.  If not, at least verify that the 13 VDC leads are wired properly.

    Remove the fuse that connects the heavy red wire to the low current relay. Connect your 13 volt power supply positive lead to the relay feeder connection and the ground to the chassis.  This lets you verify the receive and transmit synthesizers (one for each) without turning on the final amplifiers.  Your shack's 13 VDC supply probably won't have enough power for the transmitter.

    Temporarily connect a 30 gauge wire to J-702 - the VCO test point in the corner of the Delta's Control Board.

    Switch on your power supply and turn on the Control Head OFF / ON switch.  The LCD will display a frequency. 

    The Red LOCK LED on the Delta's control board will probably be lighted indicating a PLL out-of-lock condition.

    Referring to the Command Manual,  scroll down to find your radio's name and then activate it.  The external M/P will save this setting in flash memory. The Delta's PLL may or may not lock.

k) Adjusting the VCO's

    Set the frequency to 144.000 Mhz.  The RED Lock LED might extinguish.  Using a non-metallic screwdriver, adjust the Receive VCO (C220)  clockwise for about 3.5 volts on your meter.  This sets the low end of the VCO within the recommended range (3.5 - 7.5 volts) for reliable receive operation.  The external M/P will select the frequency segment based upon the frequency entered.  In my conversion, the Wideband Delta would receives up to168 Mhz, so I can listen to public service broadcasts and the weather channels.

    Reset the frequency to 144.000 Mhz.  The Transmit VCO will be adjusted next.  Depress the mike PTT switch to key the transmitter.  Your VCO might lock, but the PLL voltage level will probably be too low (mine was 2.37 volts before the adjustment and was just barely locking).  Using the proper alignment tool (I had to make one), turn the slug in L209 clockwise until the meter reads 3.5 volts, or as close as you can get before the slug 'bottoms out'.  Although I didn't have to do it, some transmit VCO's might require some additional 'padding' around L209 - 5 or 10 pf should be adequate.

    Before replacing the fuse, key the transmitter and note the time until the loop goes out of lock (i.e, stops transmitting).  This checks the software timer (CCT) programmed into the eeprom.  CCT values are, no transmitting limitation, 1/2 minute, 1 minute, etc in 30 second increments up to 3 minutes.  If your radio transmits and you are satisfied with the CCT value that the previous owner programmed into the chip, you're all set.  

    If, however, you need additional transmit time, then the eeprom will need to be reporgrammed.

    Once the Transmit VCO has been adjusted, replace the 5 amp fuse and continue to the operational tests.

Delta VHF Wideband - Low Split - 2 Meter Operation

Aside from the setting of the reference oscillator (later), these VCO's should need no adjustments as they already cover the 2 meter amateur band.
The external M/P will select the proper VCO segments based upon the frequency in use.

Delta VHF Narrowband - 2 Meters

    Ensure that the transmit and receive VCO's are optioned for the proper frequency segment. Check the service manual for additional information.      

    You'll also have to realign the Receive Oscillator Injection and Front End Helical Filters. The filters are very sharp and probably set elsewhere, so they'll need readjustment.  There's no intermod with this radio!

Delta VHF Narrowband - 6 Meters

    Ensure that you have the proper radio as the Delta Low Band radios are built in 3 ranges, 29.7 - 36 Mhz, 23 - 42 Mhz, and 42 - 50 Mhz.  Only the 42 - 50 Mhz radio will be suitable for a 6 meter conversion.  The VCO's will need to be tuned to the proper frequency, and - according to the service manual - have about a 3 Mhz maximum range.  This should be satisfactory for 6 meters as most FM activity is between 52 - 54 Mhz.

    The front end alignment of the radio may also have to be 'tweaked'. Check the Service Manual for additional information.

Delta VHF Narrowband - 10 Meters

    Check that you have the proper radio as the Delta Low Band radios are built in 3 ranges, 29.7 - 36 Mhz, 23 - 42 Mhz, and 42 - 50 Mhz.  Only the 29.7 - 36 Mhz radio will be suitable for a 10 meter conversion.  The VCO's will need to be tuned to the proper frequency, and - according to the service manual - have about a 3 Mhz maximum range.  This should be more than adequate for 10 meters.  Check the Service Manual for additional information.

    I have not converted a  Delta for 10 Meters, but the interface connections to the Delta's M/P are identical to the other conversions and should work.  The M/P has been coded for a 10 meter conversion.

Delta UHF Wideband - 440 Mhz

More information to follow....

l) Verifying Transmission

Crucial Note - Place the fuse as close to the car battery as possible.  This way, a ground on the power cable running elsewhere in the car (say, under the carpet or near the gas tank) will not burn up your car, or cause even more severe consequences!  For Delta's running close to 100 watts, use a 25 to 30 amp fuse.   For Delta's set to 45 to 60 watts, use a 15 to 20 amp unit.  Don't omit the fuse!

m) CTCSS Testing

    Turn on the radio and select a CTCSS tone frequency.    If you have another radio (like a hand held) with CTCSS capability, transmit with the same CTCSS tone selected and verify that the M/P can 'hunt' it - see the Command Manual.  Transmit with the Delta and set the tone level on the CTCSS board so that the tone activates tour hand held's receiver (when set to break the squelch when the correct CTCSS tone is received). 

n) Hitting the Road

    Mount the unit in the trunk of your car (or place it somewhere in your shack), ground the chassis to the car frame, mount your control head in a convenient spot, connect the high power leads to your car battery (again, don't forget the fuse), and you're all set to 'rock and roll'.

Note: Even though this conversion will not affect the Delta's 'spectral purity', the FCC's 'type acceptance' was voided when the radio was modified to accept the frequency agile controller.  Therefore,  it can never legally be used to transmit on non-amateur frequencies.

Connection Table


Delta Connection Points &  Connector Pins

Ferrite Beads  DB-25
M/P Board Pins

Function / 

13.2 VDC P-601 Connector
(see powering considerations)
- 3 None

 Switched DC to M/P

Ground P-601 Connector  - see text MAIN Pin 9


On / Off P-601 Connector
(see powering considerations)
- 17 N/A

Low Power Relay

SPI - Enab A-701 (M/P) - Pin 8 2 15 PLL - Pin 1 PLL Enable
SPI - Clock A-701 (M/P) - Pin 10 2 13 PLL - Pin 2 PLL Clock
SPI - Data U - 707 (Inverter) - Pin 5  2 10 PLL - Pin 3 PLL Data
Chan Chg A-701 (M/P) - Pin 33 2 14 Main Pin 6 PLL / Wideband
Transmit P-601 Connector  Pin 11 2 1 PLL - Pin 4


COR Detect P-601 Connector - Pin 12 - 5 MAIN - Pin 1 5.1 volt zener
Mike High P-601 Connector - Pin 9 2 9 N/A


Speaker P-601 Connector - Pin 18 - 19 N/A NO Ground!
Speaker P-601 Connector - Pin 20 - 20 N/A NO Ground!
Vol / Squ High P-601 Connector - Pin 7 - 25 N/A


Vol / Squ Low P-601 Connector - Pin 6 - see text N/A


Vol - Center  P-601 Connector - Pin 8 - 4 N/A

10K to 25K Control

Squ - Center  P-601 Connector - Pin 15 - 8 N/A

10K to 25K Control

CTCSS OUT Connect to J603 - Pin 15 or to channel guard board (see text) 2 18 MAIN Pin 2 Transmit CTCSS
CTCSS RCV Connect to A-701 (M/P) - Pin 29 (see text) - 2 MAIN Pin 3 Receive CTCSS
TMT OVER A-701 (M/P) - Pin 32 (see text) 2 11 JP10 - Pin 2 Transmit Override
LOCK (PLL) A-701 (M/P) - Pin 1 2 6 JP10 - Pin 1 PLL Lock Ind.

Test Table - DB-25 Cable Connections - for a Wideband Delta VHF High Split

Pin # Function R to Gnd Volts Comments
1 Delta PTT Inf 6.35 PTT Lead used to Key the Delta Radio
2 CTCSS RCV Inf 0 CTCSS from the Delta to the External M/P
3 M/P Board Power 1 M (Capacitor)
4 Volume Center Inf 4.85 Place P608  (or Strap J603 Pins 12 & 14)
5 COR (CAS) 10K 8.98 Ensure 5.1 Volt Zener Present on M/P Board
6 Lock  Inf  3.25  Delta PLL Lock Indicator
7 Ground 0 0 Chassis Ground
8 Squelch Center  Inf 0 Place P608  (or Strap J603 Pins 12 & 14)
9 Mike High 1.36K 8.99 Use a Delta / Rangr microphone
10 SPI Data 10.6K 4.85 Serial PLL Data Connection
11  TMT OVER Inf 2.49  Transmit Override (see text)
12 Ground 0 0 Chassis Ground
13 SPI Clock 10.62K 4.85 Serial PLL Clock Connection
14 Channel Change 10.64K 4.85 Enables Wideband / Fast PLL Lock
15 SPI Enable 10.69K 4.85 PLL Enable Connection
16 Ground 0 0 Chassis Ground
17 ON - OFF Switch Inf 13 Activates (Fused) Low Current Relay
18 CTCSS TMT Inf 4.46 CTCSS Lead from MX-465 to Radio
19 Speaker 40K (Capacitor) 6.60 Don't Ground
20 Speaker 40K (Capacitor) 6.84 Don't Ground
21 Ground 0 0 Chassis Ground
22 Ground 0 0 Chassis Ground
23Reserved00Reserved for Future Use
24Reserved00Reserved for Future Use
25 Vol / Squelch High Inf 0 -
Shield 'Shields' Cable 1.6 Ohm 0

G.E.and the product names Phoenix, Delta, Rangr are trademarks of Ericsson General Electric Mobile Communications.

DISCLAIMER - - If you follow the steps outlined herein, you do so at your own risk. I cannot, nor will not, be responsible for any possible damage to radio equipment, personal property, to yourself or to others caused by modifications that you may make as a result of your reading this.

The M/P controls TRANSMITTING and receiving on many frequencies, suitable for a wide range of HF, VHF and UHF needs. In the USA, TRANSMIT operation requires a license issued by the FCC  for the class of operation intended.  Amateur radio licensees must maintain strict control over their equipment, preventing unlicensed operation within or outside of the amateur bands.

Copyright 2010 - K3JLS